Preparation method of CF / PPS composite material with high compression strength

Abstract

The application relates to a preparation method of a CF / PPS composite material with high compression strength. First, a PPS film and a carbon fiber fabric are laminated and laid into a mold A, the temperature is raised to 330-350 DEG C at a speed of 30-50 / min under pressure to make the PPS melt and form a CF / PPS composite material blank, then the CF / PPS composite material blank is heated to obtain a softened blank at a speed of 30-100 DEG C / min, and finally the softened blank is transferred to a mold B with a certain temperature to be punched and formed to obtain the CF / PPS composite material with high compression strength; the temperature of the mold B is 75-95 DEG C lower than that of the softened blank. The preparation method of the CF / PPS composite material with high compression strength improves the crystallization temperature and the crystallization rate of the CF / PPS composite material through a special heat history, and the compression performance of the CF / PPS composite material is enhanced due to the change of the crystallization morphology.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of polymer material processing, and relates to a preparation method of a CF / PPS composite material with high compressive strength. BACKGROUND

[0002] Advanced thermoplastic composites represented by CF / PPS have attracted extensive attention due to their fast molding cycle, recyclability and repairability. PPS is composed of benzene rings and sulfur atoms alternately, and has excellent thermal stability, chemical resistance and friction performance. Therefore, carbon fiber reinforced polyphenylene sulfide composites are suitable for aerospace, automobile, electronics, machinery, ship and other fields.

[0003] Due to the secondary forming characteristics of thermoplastic composites, CF / PPS composites can be formed by stamping and 3D printing. Among them, the stamping forming of CF / PPS composite materials is widely used, especially suitable for the manufacturing of parts in the fields of automobile and aerospace. For example, manufacturing automobile door inner plate, roof, front bumper, etc., and aircraft body parts, turbine engine blades, etc. in the field of aerospace. Compared with traditional metal materials, CF / PPS composite materials have higher strength, lighter weight and better corrosion resistance, which can effectively reduce the weight of parts and improve the durability and service life of materials.

[0004] However, the compressive performance of CF / PPS composite materials is low, which limits the application of the materials.

[0005] In order to improve the compressive performance of CF / PPS composite materials, the following methods are often used:

[0006] The surface of carbon fiber is treated by using sizing agent to improve the interfacial bonding force between fiber and resin. The main methods are as follows: specific functional groups are added on the fiber through chemical modification to form bonding force with the molecular chain of the matrix; for example, the literature (High performance thermoplastic polymer for the compressive behaviourof carbon fibre reinforced composites[J]. Pigment & Resin Technology, 2021, 50(5): 426-436.) coats silane coupling agent on the surface of CF to form an effective transition layer with PPS, thereby enhancing the interfacial interaction between CF and PPS, and finally increasing the compressive strength of CF / PPS composite material to 355MPa. However, this method needs to use additional additives and additional processing steps, which increases the processing cost. And the compressive performance obtained finally still needs to be improved.

[0007] Therefore, it is of great significance to study a method for improving the compression performance of the CF / PPS composite material. SUMMARY

[0008] To solve the problems in the prior art, the application provides a preparation method of a CF / PPS composite material with high compression strength.

[0009] To achieve the above-mentioned purposes, the application adopts the following solutions:

[0010] The preparation method of the CF / PPS composite material with high compression strength comprises the following steps: firstly, PPS film and carbon fiber fabric are laminated and laid into a mold A, and under the condition of pressurization, the temperature is raised to 330-350 DEG C at a rate of 30-50 / min to make the PPS melt and cool to form a CF / PPS composite material blank; then, the CF / PPS composite material blank is heated to obtain a softened blank at a rate of 30-100 DEG C / min to 290-300 DEG C; finally, the softened blank is transferred to a mold B with a certain temperature, and is stamped and formed to obtain the CF / PPS composite material with high compression strength.

[0011] The temperature of the mold B is 75-95 DEG C lower than that of the softened blank; if the temperature of the mold B is too low, the cooling rate of the blank is too fast, the ductility of the blank is poor during the forming process, and the blank will wrinkle and other defects during the forming process, thereby affecting the appearance and performance of the composite material; if the temperature of the mold is too high, the composite material is prone to transverse deformation during the forming process, thereby affecting the thickness and appearance of the material;

[0012] The pressure required for the stamping and forming is 0.6-2 MPa.

[0013] As a preferred technical solution:

[0014] The preparation method of the CF / PPS composite material with high compression strength as described above, and the compression strength of the CF / PPS composite material with high compression strength is 580-630 MPa.

[0015] The preparation method of the CF / PPS composite material with high compression strength as described above, and the compression strength of the CF / PPS composite material with high compression strength is 580-630 MPa.

[0016] (1) PPS film and carbon fiber fabric are laminated into mold A, and heated to 330-350°C at a rate of 30-50 / min under pressure, and kept for a period of time, so that PPS film is completely melted, and the melted PPS is fully impregnated into the carbon fiber under the action of pressure; if the hot-pressing temperature is less than 330°C, the viscosity of PPS is too high, which will result in that PPS cannot be fully impregnated into the fiber, thus causing defects such as porosity; if the hot-pressing temperature is greater than 350°C, the viscosity of PPS decreases, and too much PPS is overflowed in the mold pressing, thus causing the fiber volume content to be too high, and resulting in the decrease of the mechanical properties of the material; the heating rate <30°C / min will result in that PPS stays at high temperature for too long time during the heating process, which will result in the thermal oxidation crosslinking reaction of PPS, and the linear structure of PPS molecular chain will be destroyed, thus resulting in the decrease of the material properties;

[0017] (2) mold A is cooled to 20-100°C, so that PPS is crystallized and solidified, and a CF / PPS composite material blank is obtained;

[0018] (3) mold A is heated again to 290-300°C at a rate of 30-100°C / min, and kept for a period of time, so that the polymer spherulites in the composite material are melted to form small residual crystal grains or locally ordered regions of molecular chains, which become nucleation sites for the next crystallization, and a softened blank is obtained; if the temperature is greater than 300°C, the spherulites will be completely melted, and the locally ordered regions will be destroyed by the thermal motion of molecular chains and become disordered, thus cannot become self-nucleation sites for the next crystallization; if the temperature is less than 290°C, the spherulites will not be melted, and can only be annealed to form irregular spherulites, thus cannot form self-nucleation sites, and thus cannot change the crystalline structure in the composite material; the heating rate <30°C / min will result in that PPS stays at high temperature for too long time during the heating process, which will result in the thermal oxidation crosslinking reaction of PPS, and the linear structure of PPS molecular chain will be destroyed, thus resulting in the decrease of the material properties;

[0019] (4) the softened blank is transferred to mold B with a temperature of 205-225°C, a certain pressure is applied, and kept for a period of time, and because the mold temperature is lower than the blank temperature, the blank is rapidly cooled by heat transfer, and is crystallized and solidified to form a CF / PPS composite material with high compressive strength after the mold is opened. If the temperature of mold B is too low, the cooling rate of the blank is too fast, the blank becomes hard rapidly during the molding process, the ductility is poor, the blank will wrinkle during the molding, and the appearance and properties of the composite material are affected; if the mold temperature is too high, the composite material is prone to transverse deformation during the molding, the thickness of the material is thinned, and the appearance and properties are affected.

[0020] The preparation method of the CF / PPS composite material with high compression strength as described above, wherein the volume ratio between the PPS film and the carbon fiber fabric in step (1) is 35:65-45:55.

[0021] The preparation method of the CF / PPS composite material with high compression strength as described above, wherein the pressure in step (1) is 6-12 MPa, and the holding time is 5-10 min.

[0022] The preparation method of the CF / PPS composite material with high compression strength as described above, wherein the cooling rate in step (2) is less than 50 DEG C / min, so that the PPS crystallization in the composite material is saturated.

[0023] The preparation method of the CF / PPS composite material with high compression strength as described above, wherein the holding time in step (3) is 5-10 min.

[0024] The preparation method of the CF / PPS composite material with high compression strength as described above, wherein the pressure in step (4) is 1-2 MPa, and the holding time is 60-200 s.

[0025] The principle of the present application is as follows:

[0026] In the composite material, the combination of the polymer and the fiber forms an interface, and the interface performance will greatly affect the mechanical properties of the composite material.

[0027] In more detail, the contact between the fiber and the polymer at the interface is divided into two categories: one is that the polymer body crystallizes, and the crystalline edge contacts the spherulite, and the interaction force is weak. The other is that the fiber surface nucleates and crystallizes, and since the crystallization is directly grown on the fiber surface as a substrate, the interaction force between the fiber and the polymer at the interface is strong.

[0028] Since the semi-crystalline polymer such as PPS has weak polarity and poor compatibility with carbon fibers, the nucleation sites of the fiber are few, and the crystals grown from the nucleation sites on the fiber surface are few, which leads to weak bonding between the matrix and the fiber at the interface, limiting the mechanical properties of the composite material.

[0029] The material prepared by the existing process (one is to experience a temperature rise and fall in a molding machine, and the final material is obtained by molding. The other is to experience two temperature rises and falls, although it also experiences two temperature rises and falls, but this existing process only considers melting and cooling of the material, and the control of the crystal morphology and structure has been ignored.) Since the compatibility between the fiber and the polymer is poor, the nucleation sites on the fiber surface are few, which leads to few crystals on the fiber surface, which will lead to small direct interaction area between the fiber and the matrix, so the bonding between the matrix and the fiber at the interface is weak.

[0030] The present application controls the temperature rise rate, melt temperature and holding time in the first temperature rise process, so that the PPS is completely melted, and the melted PPS is fully impregnated into the carbon fiber under the action of pressure, while avoiding the occurrence of adverse reactions such as thermal oxidation of PPS at high temperature for too long time. Then, by controlling the temperature rise rate, melt temperature and holding time in the second temperature rise process, the PPS matrix and the crystal on the surface of CF are melted, but residual grains and local ordered structure of molecular chains are still retained in the melt, which can promote the crystallization nucleation process in the second cooling process due to the low entropy value, and increase the nucleation density on the surface of CF. In addition, by transferring to the mold and applying appropriate pressure, the composite material is compacted again in the process of secondary molding, reducing the porosity of the composite material. At the same time, in the cooling process, the PPS on the surface of CF begins to crystallize, and since the nucleation density is increased, the direct interaction area between CF and PPS crystals is increased, which improves the bonding between the fiber and the resin at the interface, and finally improves the compression performance of the CF / PPS composite material.

[0031] Advantages

[0032] (1) The preparation method of the CF / PPS composite material with high compression strength of the present application improves the crystallization temperature and crystallization rate of the CF / PPS composite material through a special thermal history, and at the same time, the compression performance of the CF / PPS composite material is enhanced due to the change of the crystal morphology;

[0033] (2) The application discloses a preparation method of a CF / PPS composite material with high compression strength. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 A micrograph of the CF / PPS composite materials prepared in Comparative Example 4 and Example 5; wherein the left graph is the CF / PPS composite material prepared in Comparative Example 4, and the right graph is the CF / PPS composite material prepared in Example 5;

[0035] Figure 2 A comparison graph of the crystallization temperatures of the CF / PPS composite materials of Comparative Example 4 and Example 5;

[0036] Figure 3 A comparison graph of the compression strengths of the CF / PPS composite materials of Comparative Example 4 and Example 5 at room temperature. DETAILED DESCRIPTION

[0037] The application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the application and not used to limit the scope of the application. In addition, it should be understood that those skilled in the art can make various modifications or changes to the application after reading the content of the application, and these equivalent forms also fall within the scope of the appended claims of the application.

[0038] The test method used in the application is as follows:

[0039] Compression strength: the compression performance test is performed according to the ASTM D3039 standard. The sample size is 140 mm x 13 mm x 2.5 mm, and the two ends are respectively bonded with reinforcing sheets. In order to measure the strain, a strain gauge with a length of 6 mm is bonded to the center of each sample. The test uses a universal testing machine (MTS), and the test rate is 1 mm / min.

[0040] In the embodiments of the application, the PPS film manufacturer is Zhejiang Xinhengcheng Co., Ltd., and the product brand is 3518. The PPS powder is obtained by crushing the PPS film. The carbon fiber fabric manufacturer is Toray Industries, Inc., and the product brand is T300J-5HS.

[0041] Example 1

[0042] A preparation method of a CF / PPS composite material with high compression strength, and the specific steps are as follows:

[0043] (1) PPS film and carbon fiber fabric were stacked and laid into mold A, and heated to 330℃ at a rate of 30℃ / min under a pressure of 6 MPa, and kept for 5 min; the volume ratio between PPS film and carbon fiber fabric was 35:65;

[0044] (2) mold A was cooled to 20℃ at a rate of 48℃ / min, to obtain a CF / PPS composite material blank;

[0045] (3) mold A was heated again to 290℃ at a rate of 50℃ / min, and kept for 10 min, to obtain a softened blank;

[0046] (4) the softened blank was transferred to mold B at a temperature of 205℃, a pressure of 1 MPa was applied, and kept for 200 s, and a CF / PPS composite material with high compressive strength was obtained after mold opening.

[0047] The crystallization temperature of the obtained CF / PPS composite material with high compressive strength was 252.3℃, and the compressive strength was 580 MPa.

[0048] Comparative Example 1

[0049] A method for preparing a CF / PPS composite material, which was basically the same as Example 1, except that the temperature of mold B in step (4) was 260℃.

[0050] The compressive strength of the obtained CF / PPS composite material was 425 MPa.

[0051] Compared with Example 1, the compressive performance of Comparative Example 1 was sharply reduced, because the temperature of mold B was too high, which resulted in that the blank could not be rapidly cooled in mold B, and the blank was severely deformed in the transverse direction when the pressure was applied, the fibers in the material were arranged in disorder, and the compressive performance was seriously affected.

[0052] Comparative Example 2

[0053] A method for preparing a CF / PPS composite material, which was basically the same as Example 1, except that the temperature of mold B in step (4) was 150℃.

[0054] The compressive strength of the obtained CF / PPS composite material was 412 MPa.

[0055] Compared with Example 1, the compressive performance of Comparative Example 2 was sharply reduced, because the temperature of mold B was too low, the blank was rapidly cooled, and the plasticity was poor, which resulted in that the blank was wrinkled and other defects occurred during molding, and the compressive performance of the composite material was affected.

[0056] Comparative Example 3

[0057] A method for preparing a CF / PPS composite material, which is substantially the same as that of Example 1, except that step (4) is not transferred to mold B, but is performed in mold A for secondary cooling.

[0058] The compression strength of the prepared CF / PPS composite material is 503 MPa.

[0059] Compared with Example 1, the compression performance of Comparative Example 3 is reduced, because the process of transferring step (4) to mold B for re-pressing can complete the re-impregnation of CF / PPS, so that the porosity of the plate is further reduced. Due to the lack of step (4), the material does not undergo the re-impregnation process, resulting in a decrease in the compression performance of the material.

[0060] Example 2

[0061] A method for preparing a CF / PPS composite material with high compression strength, the specific steps are as follows:

[0062] (1) PPS film and carbon fiber fabric are stacked and laid in mold A, and the temperature is raised to 330℃ at a rate of 35℃ / min under a pressure of 7 MPa, and the temperature is maintained for 6 min; wherein the volume ratio between PPS film and carbon fiber fabric is 36:64;

[0063] (2) The mold A is cooled to 30℃ at a rate of 46℃ / min to obtain a CF / PPS composite material blank;

[0064] (3) The mold A is heated again to 292℃ at a rate of 60℃ / min, and the temperature is maintained for 9 min to obtain a softened blank;

[0065] (4) The softened blank is transferred to mold B with a temperature of 210℃, and a pressure of 1.1 MPa is applied, and the temperature is maintained for 160 s, and after the mold is opened, a CF / PPS composite material with high compression strength is prepared.

[0066] The crystallization temperature of the prepared CF / PPS composite material with high compression strength is 252.3℃, and the compression strength is 586 MPa.

[0067] Example 3

[0068] A method for preparing a CF / PPS composite material with high compression strength, the specific steps are as follows:

[0069] (1) PPS film and carbon fiber fabric are stacked and laid in mold A, and the temperature is raised to 335℃ at a rate of 35℃ / min under a pressure of 8 MPa, and the temperature is maintained for 6 min; wherein the volume ratio between PPS film and carbon fiber fabric is 38:62;

[0070] (2) The mold A is cooled at a rate of 45℃ / min to 40℃ to obtain a CF / PPS composite material blank;

[0071] (3) The mold A is heated again at a rate of 70℃ / min to 294℃ and kept for 8min to obtain a softened blank;

[0072] (4) The softened blank is transferred to the mold B with a temperature of 213℃, a pressure of 1.3MPa is applied, and kept for 140s, and a CF / PPS composite material with high compressive strength is obtained after the mold is opened.

[0073] The crystallization temperature of the prepared CF / PPS composite material with high compressive strength is 252.3℃, and the compressive strength is 591MPa.

[0074] Example 4

[0075] A method for preparing a CF / PPS composite material with high compressive strength, the specific steps are as follows:

[0076] (1) The PPS film and carbon fiber fabric are stacked and laid into the mold A, heated to 335℃ at a rate of 40℃ / min under a pressure of 9MPa, and kept for 7min; wherein the volume ratio between the PPS film and the carbon fiber fabric is 40:60;

[0077] (2) The mold A is cooled at a rate of 40℃ / min to 50℃ to obtain a CF / PPS composite material blank;

[0078] (3) The mold A is heated again at a rate of 80℃ / min to 296℃ and kept for 7min to obtain a softened blank;

[0079] (4) The softened blank is transferred to the mold B with a temperature of 215℃, a pressure of 1.5MPa is applied, and kept for 120s, and a CF / PPS composite material with high compressive strength is obtained after the mold is opened.

[0080] The crystallization temperature of the prepared CF / PPS composite material with high compressive strength is 252.5℃, and the compressive strength is 623MPa.

[0081] Example 5

[0082] A method for preparing a CF / PPS composite material with high compressive strength, the specific steps are as follows:

[0083] (1) PPS film and carbon fiber fabric are laminated into mold A, and heated to 340℃ at a rate of 40℃ / min under a pressure of 10 MPa, and kept for 8 min; the volume ratio between PPS film and carbon fiber fabric is 42:58;

[0084] (2) mold A is cooled to 60℃ at a rate of 35℃ / min, to obtain a CF / PPS composite material blank;

[0085] (3) mold A is heated to 297℃ at a rate of 85℃ / min, and kept for 6 min, to obtain a softened blank;

[0086] (4) the softened blank is transferred to mold B at a temperature of 220℃, a pressure of 1.7 MPa is applied, and kept for 100 s, to obtain a CF / PPS composite material with high compressive strength after mold opening.

[0087] The CF / PPS composite material with high compressive strength has a crystallization temperature of 252.6℃ and a compressive strength of 628 MPa.

[0088] Comparative Example 4

[0089] A method for preparing a CF / PPS composite material, which is basically the same as Example 5, except that steps (3) and (4) are omitted, and step (2) is kept for 100 s after cooling.

[0090] The CF / PPS composite material has a crystallization temperature of 233.2℃ and a compressive strength of 492 MPa.

[0091] Compared with Example 5, the crystallization temperature of Comparative Example 4 is reduced, and the compressive performance is reduced, because the CF / PPS composite material does not undergo a second heating process, and there is no residual grain or ordered structure region in the material caused by the second heating process, so the PPS nucleation density on the surface of CF is not increased, resulting in a small direct interaction area of CF and PPS crystals, and a reduced interfacial bonding capacity, which ultimately leads to a lower compressive performance.

[0092] As shown in Figure 1 , the left side is a microstructure diagram of the composite material prepared by the process in Comparative Example 4. The crystalline number grown on the fiber surface with high interfacial bonding strength of the composite material is small due to the small nucleation site on the fiber surface, resulting in a small direct interaction area of the fiber and the matrix at the interface. The right side is a microstructure diagram of the composite material prepared by the process in Example 5 of the present application. The present application increases the nucleation density on the fiber surface of the composite material, increases the number of crystalline grown on the fiber surface, and directly increases the direct interaction area of the fiber and the matrix, thereby improving the bonding condition of the fiber and the resin at the interface.

[0093] AsFigure 2 As shown, the present application increases the crystallization temperature of the CF / PPS composite material by more than 19℃, so that the CF / PPS composite material has a faster crystallization speed in the stamping process. In addition, as shown, the CF / PPS composite material prepared by the present application has a significantly improved compressive strength at room temperature. Compared with the CF / PPS composite material plate prepared in Comparative Example 4, the compressive strength of the CF / PPS composite material plate prepared by the present application reaches 628.0 MPa, which is increased by 27.6%. Figure 3 As shown, the CF / PPS composite material prepared by the present application has a significantly improved compressive strength at room temperature. Compared with the CF / PPS composite material plate prepared in Comparative Example 4, the compressive strength of the CF / PPS composite material plate prepared by the present application reaches 628.0 MPa, which is increased by 27.6%.

[0094] Example 6

[0095] A method for preparing a CF / PPS composite material with high compressive strength, the specific steps are as follows:

[0096] (1) The PPS film and carbon fiber fabric are stacked and laid into mold A, and heated to 345℃ at a rate of 45℃ / min under a pressure of 11MPa, and kept for 9min; wherein the volume ratio between the PPS film and the carbon fiber fabric is 44:56;

[0097] (2) The mold A is cooled to 80℃ at a rate of 30℃ / min to obtain a CF / PPS composite material blank;

[0098] (3) The mold A is heated again to 298℃ at a rate of 90℃ / min, and kept for 5min to obtain a softened blank;

[0099] (4) The softened blank is transferred to mold B with a temperature of 223℃, and a pressure of 1.9MPa is applied, and kept for 80s, and a CF / PPS composite material with high compressive strength is prepared after the mold is opened.

[0100] The crystallization temperature of the prepared CF / PPS composite material with high compressive strength is 251.4℃, and the compressive strength is 607MPa.

[0101] Example 7

[0102] A method for preparing a CF / PPS composite material with high compressive strength, the specific steps are as follows:

[0103] (1) The PPS film and carbon fiber fabric are stacked and laid into mold A, and heated to 345℃ at a rate of 45℃ / min under a pressure of 11MPa, and kept for 9min; wherein the volume ratio between the PPS film and the carbon fiber fabric is 44:56;

[0104] (2) The mold A is cooled to 80℃ at a rate of 30℃ / min to obtain a CF / PPS composite material blank;

[0105] (3) The mold A is heated again to 300℃ at a rate of 100℃ / min, and kept for 5 min, to obtain a softened blank;

[0106] (4) The softened blank is transferred to the mold B with a temperature of 225℃, a pressure of 2 MPa is applied, and kept for 60 s, and the CF / PPS composite material with high compressive strength is obtained after the mold is opened.

[0107] The crystallization temperature of the obtained CF / PPS composite material with high compressive strength is 250.6℃, and the compressive strength is 593 MPa.

Claims

1. A method for preparing a CF / PPS composite material with high compressive strength, characterized in that, The specific steps are as follows: (1) PPS film and carbon fiber fabric are laminated into mold A, and the temperature is raised to 330-350℃ at a rate of 30-50℃ / min under pressure, and kept at the temperature and pressure for a period of time. (2) Cool mold A to 20~100℃ to allow PPS to crystallize and solidify, and obtain CF / PPS composite material blank; (3) The mold A is heated again to 290-300℃ at a rate of 30-100℃ / min and kept at that temperature for a period of time to obtain a softened blank; (4) Transfer the softened blank to mold B at a temperature of 205~225℃. The temperature of mold B is 75~95℃ lower than the temperature of the softened blank. Apply a certain pressure of 0.6~2MPa and keep it warm and pressurized for a period of time. After opening the mold, a CF / PPS composite material with high compressive strength is obtained. The compressive strength of CF / PPS composite materials with high compressive strength is 580~630MPa.

2. The method for preparing a CF / PPS composite material with high compressive strength according to claim 1, characterized in that, In step (1), the volume ratio between the PPS film and the carbon fiber fabric is 35:65~45:

55.

3. The method for preparing a CF / PPS composite material with high compressive strength according to claim 1, characterized in that, In step (1), the pressure applied is 6~12MPa, and the heat preservation and pressure holding time is 5~10min.

4. The method for preparing a CF / PPS composite material with high compressive strength according to claim 1, characterized in that, The cooling rate in step (2) is less than 50℃ / min.

5. The method for preparing a CF / PPS composite material with high compressive strength according to claim 1, characterized in that, The heat preservation time in step (3) is 5~10 minutes.

6. The method for preparing a CF / PPS composite material with high compressive strength according to claim 1, characterized in that, The pressure applied in step (4) is 1~2MPa, and the heat preservation and pressure holding time is 60~200s.

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